1. Field of the Invention
The present invention relates to the rocker arm mechanism in the overhead cam type engine (hereinafter referred to as "OHC" type engine) such that in the OHC type engine in which the cams are positioned over the cylinder head, the rotary driving motion of the cams is transformed into the reciprocating motion of the intake and exhaust valves via the rocker arms.
2. Description of the Prior Art
There have been conventionally available the following rocker arms:
(1) an integral type rocker arm, whole parts of which are made of the same material, PA1 (2) a composite type rocker arm in which the rock arm body and the pad member constituting the cam contact portion made of different material respectively are integrated by way of brazing, welding or the like, and PA1 (3) an encasting type rocker arm in which the above pad member is encast by aluminum or alluminum alloy.
However, all of these rocker arms are liable to suffer from scuffing and/or excessive wear at the portion of the rocker arms where they contact the cams, resulting in the generation of unnecessary noise and reduction in engine output.
As countermeasures against these unfavourable phenomena, recently the above composite type or encast type rocker arm with the pad member made of excellent wear-resistant material has come to be employed, but are not necessarily satisfactory. In particular, they are completely unsatisfactory when employed in the diesel engine.